1. Field of the Invention
The present invention relates to a substrate of glass, ceramics, plastic, or metal, etc., having a treatment surface, i.e., a water repellent coating or film being formed on an undercoating layer or film thereof, and a treatment method therefor.
2. Description of Related Art
Conventionally, a substrate comprising for example glass or the like, on the surface of which a water repellent coating, layer or film is formed, has been already known, in for example, Japanese Patent Publication No. Hei 4-20781 (1992), Japanese Laid-open Patent No. Hei 5-86353 (1993), Japanese Laid-open Patent No. Hei 5-161844 (1993), Japanese Laid-open Patent No. Hei 2-311332 (1990) and Japanese Patent No. 2,525,536.
In Japanese Patent Publication No. Hei 4-20781 (1992), it is disclosed that on the surface of the substrate there is formed a coating layer or film from a silane compound excluding polyfluoro radicle or synthetic resin, and further thereon is formed a water repellent and oil repellent multi-layer coating or film comprising a silane compound including polyfluoro radicle.
Further, in Japanese Laid-open Patent No. Hei 5-86353 (1993), there is disclosed a method by which a thin film of siloxan radicle is formed on the surface of glass, ceramics, plastic, or metal, etc., by use of a compound including chlorosilyl radicle, such as SiCl4, in molecular form thereof, and further thereon is formed a chemical absorption unimolecular accumulation layer or film (a water repellent film or coating).
Also in Japanese Laid-open Patent No. Hei 5-161844 (1993), there is described a method in which, having formed a unimolecular film of siloxan radicle or an absorption film of polysiloxan previously, the chemical absorption unimolecular film (a water repellent film or coating) is formed on the surface of a substrate by a further chemical absorption processing conducted in an atmosphere including a surface-active agent of chlorosilane radicle.
Moreover, Japanese Laid-open Patent No. Hei 2-311332 (1990) describes a water repellent glass obtained through silylating the surface of glass substrate by a silyl compound, such as fluorinated alkylsilane, the surface of which is formed from a metal oxide, such as SiO2.
Furthermore, Japanese Patent No. 2,523,536 discloses that an undercoating film or layer of silica is applied on the glass substrate before treating the surface thereof by the fluorine compound, in the same manner as described in Japanese Laid-open Patent No. Hei 2-311332 (1990), and further that weather resistance of the water repellent film is improved by including olefin telomer in the fluorine compound.
With the substrate which can be obtained by the method disclosed in Japanese Patent Publication No. Hei 4-20781 (1992), since the density of the undercoating layer is low, the undercoating layer must be more than 100 nm in thickness thereof and also the temperature for baking must be higehr than 400xc2x0 C.
In the method disclosed in Japanese Laid-open Patent No. Hei 5-86353 (1993), since the absorbent for the reaction to water in air is unstable, it is necessary to maintain the humidity in the atmosphere low, thereby control of the environment being difficult. Further, there are problems, in that it takes 2-3 hours for the treatment, and the nonaqueous solvent is expensive.
For implementation of the method which is disclosed in Japanese Laid-open Patent No. Hei 5-161844 (1993), equipment for controlling the atmosphere must be large-scaled, and it takes time to form a perfect absorption film.
With the substrate which is obtained by the method disclosed in Japanese Laid-open Patent No. Hei 2-311332 (1990), since baking at 500xc2x0 C. for instance is necessitated for obtaining the high density metal oxide layer when forming the metal oxide film through a sol-gel method, also large-scaled equipment for baking the substrate at high temperature is necessary, thus raising the production cost. Further, having tried this method, the roughness of the metal oxide film thereby obtained is relatively high, resulting that it is difficult for water drops present on the surface of the water repellent glass to roll freely thereon.
Furthermore, with the substrate which is obtained by the method disclosed in Japanese Patent No. 2,525,536, though being superior with respect to weather resistance, such a result is only obtained through double-checking thereof that the durability of the water repellent film in a friction test is not adequate, and it is also difficult for water drops present on the surface of the water repellent glass to roll freely thereon since the roughness of the surface of the silica undercoating layer or coating is relatively high.
For resolving the drawbacks in the conventional art mentioned above, according to the present invention, there is provided a substrate having a treatment surface, characterized in that, on a surface of a substrate of glass, ceramics, plastics or metal, an undercoating film layer is formed by drying a liquid for undercoating treatment which is obtained by dissolving and reacting a material having chlorosilyl radicle in molecular form therein within an alcohol group solvent, so that on said undercoating film layer there is formed a water repellent or oil repellent layer, wherein a surface roughness (Ra) of said surface layer is equal to or less than 0.5 nm.
Further, the surface roughness (Ra) of the surface layer is preferably to be as small as possible. However, for example, the surface roughness (Ra) of a fire polished surface of float glass (i.e., upper surface of the float glass floating on molten tin) is about 0.2 nm, and the roughness (Ra) of a glass surface obtained through precise grinding is about 0.1 nm. Therefore, the substantially lowest threshold value of surface roughness (Ra) of the glass surface which can be obtained is about 0.1-0.2 nm.
As mentioned above, the undercoating film or layer formed from the undercoating treatment liquid, which is obtained by dissolving and reacting the material having chlorosilyl radicle in molecular form therein within an alcohol group solvent, has high smoothness, and therefore, the surface layer formed on the undercoating film or layer also comes to have high smoothness (Raxe2x89xa60.5 nm), reflecting the smoothness of the undercoating layer, thereby obtaining a superior water repellent property, i.e., a high contact angle and a low critical inclination angle.
Here, it is possible to remove defects in appearance by keeping the surface of the substrate clean when forming the undercoating layer or film on it, and it is also possible to increase adhesive strength between the substrate surface and the undercoating film by activating the surface of the substrate. For example, even in a case where the glass substrate comprises an oxide, it is possible to form an active surface by grinding the surface to within 0.5 nmxe2x89xa6Raxe2x89xa63.0 nm using a grinding agent.
However, in the case where the roughness (Ra) of the substrate surface exceeds 3.0 nm, it is difficult to make the roughness (Ra) of the surface layer (the water repellent layer) less than 0.5 nm even if effecting the undercoating treatment thereon. Therefore, it is preferable that the roughness (Ra) of the substrate surface be equal to or less than 3.0 nm. Moreover, when the substrate is made of glass plate, transparency of the substrate can be maintained when the roughness (Ra) is within a range of 0.5 nm=Raxe2x89xa63.0 nm.
Further, in the case where hydrophilic radicle is poor in the surface of the substrate, it is preferable to conduct the surface treatment after treatment for hydrophilizing the surface, i.e., by treating the surface with plasma containing oxygen or treating under a corona discharge atmosphere, or alternatively, by irradiating ultraviolet light of a wavelength in the vicinity of from 200 to 300 nm onto the substrate surface in an atmosphere containing oxygen.
Further, according to the present invention, it is appropriate to restrict the concentration of the material having chlorosilyl radicle in molecular form therein within the liquid for the undercoating treatment, this being equal to or greater than 0.01 wt % and equal to or less than 3.0 wt %.
As an example of a material having chlorosilyl radicle radicle in molecular form therein, there can be listed SiCl4, SiHCl3 or SiH2Cl2, etc., and it is possible to select a single or a plurality of materials from among these as the material. In particular, since it contains the most Cl radicles, SiCl4 is preferable. The chlorosilyl radicle is very high in reactivity thereof, and it forms a minute or dense undercoating film through a self-condensation reaction or by reaction to the substrate surface. However, it can contain a material in which a part of a hydrogen is replaced by methyl radicle or ethyl radicle.
Further, as the alcohol group sovlent, for example, methanol, ethanol, 1-propanol, and 2-propanol are desirable. The material containing chlorosilyl radicle in molecular form therein and the alcohol group solvent, as is shown by equation (1) below, react to form alkoxide by removing hydrogen chloride:
(xe2x80x94Sixe2x80x94Cl)+(ROH)xe2x86x92(xe2x80x94Sixe2x80x94OR)+(HCl) xe2x80x83xe2x80x83(1) 
Further, the material containing chlorosilyl radicle in molecular form therein and the alcohol group solvent react as shown by equation (2) below:
(xe2x80x94Sixe2x80x94Cl)+(ROH)xe2x86x92(xe2x80x94Sixe2x80x94OH)+(RCl) xe2x80x83xe2x80x83(2) 
In the alcohol solvent, a part of (xe2x80x94Sixe2x80x94OR) reacts as shown by equation (3) below with an acidic catalyst which is formed as shown by equation (1), and forms (xe2x80x94Sixe2x80x94OH).
(xe2x80x94Sixe2x80x94OR)+(H2O)xe2x86x92(xe2x80x94Sixe2x80x94OH)+(ROH) xe2x80x83xe2x80x83(3) 
In addition, (xe2x80x94Sixe2x80x94OH) which is produced as shown by the above equations (2) and (3) reacts as shown by equation (4) below, and forms siloxane bonding:
(xe2x80x94Sixe2x80x94Cl)+(xe2x80x94Sixe2x80x94OH)xe2x86x92(xe2x80x94Sixe2x80x94Oxe2x80x94Sixe2x80x94)+(HCl) xe2x80x83xe2x80x83(4) 
It is considered that, by means of the above-mentioned siloxane bonding, the bonding between the substrate and the undercoating film, or between the undercoating film and the surface film such as the water repellent film is strengthened. Namely, in the case where a compound including the siloxane bonding is simply used as the liquid for the undercoating treatment as disclosed in the conventional arts, though the siloxane bonding exists within the undercoating film, the siloxane bonding joining between the substrate and the undercoating film, or between the undercoating film and the water repellent film, are not so influential.
According to the present invention, by treating with a liquid for performing an undercoating treatment which is obtained by reacting the material having chlorosilyl radicle radicle in molecular form in the alcohol group solvent within thirty (30) minutes after mixing thereof, an undercoating film being superior in smoothness can be formed, and since a part of the chlorosyl radicle takes part in the siloxane bonding, good bonding between the substrate and the water repellent film can be obtained by the siloxane bonding.
Here, it is preferable that the concentration of the material having chlorosilyl radicle in molecular form therein contained in the undercoating treatment liquid, though depending on the method of coating be equal to or greater than 0.01 wt % and equal to or less than 3.0 wt %. If it is lower than that, no effect by adding the material can be obtained, and if higher than that, the effect of adding the material is not improved. For example, in particular, in the case of coating by using, for example, a curtain flow coating method, judging from the appearance during the coating, it is preferable that the concentration be equal to or greater than 0.3 wt % and equal to or less than 1.0 wt %.
The method for coating the undercoating treatment liquid should not be limited in particular. However, other methods can be listed, such as: a dip coating method, a curtain flow coating method, a spin coating method, a bar coating method, a roll coating method, a hand coating method, a brush painting method, a spray coating method, etc.
Further, as the surface treatment, for instance, a water repellent treatment and an oil repellent treatment can be listed. Though the liquid agents for the water and oil repellent treatments should not be limited in particular, a treating method by using water repellent or oil repellent agents containing silane compound, siloxane compound or silicon compound therein is preferable.
As the silane compound, there can be listed water repellent agents containing:
CF3(CF2)7(CH2)2Si(OCH3)3,
CF3(CF2)6(CH2)2Si(OCH3)3,
CF3(CF2)7(CH2)2SiCl3,
CF3(CF2)6(CH2)2SiCl3, and the like.
These repellent agents can be used, depending on necessity, by being hydrolyzed using a catalyst such as acid or base. Further, an agent, containing the siloxane compound which can be obtained through hydrolysis or condensation of the silane compound, can be used too.
As the silicon compound there can be used polydimethylsiloxane of straight chain or chain form, or silanol metamorphism, alkoxide metamorphism, hyrogen metamorphism, halogen metamorphism thereof, etc.
For the method for the water repellent or oil repellent treatment, in the same manner as the undercoating treatment, though it should not be limited in particular, methods such as the hand coating method, the brush painting method, etc., can be applied thereto.
Further, as the surface treatment according to the present invention, a hydrophilic treatment or an antifogging treatment can be applied, in addition to the water repellent or oil repellent treatment.